U.S. patent application number 17/421149 was filed with the patent office on 2022-03-10 for isoprene-based polymer latex composition.
This patent application is currently assigned to SHOWA DENKO K.K.. The applicant listed for this patent is SHOWA DENKO K.K.. Invention is credited to Masanao KAMIJO, Tomoaki MURATA, Masahiro OGAWA, Noriko OGAWA.
Application Number | 20220073657 17/421149 |
Document ID | / |
Family ID | 71521176 |
Filed Date | 2022-03-10 |
United States Patent
Application |
20220073657 |
Kind Code |
A1 |
OGAWA; Masahiro ; et
al. |
March 10, 2022 |
ISOPRENE-BASED POLYMER LATEX COMPOSITION
Abstract
An isoprene-based polymer latex composition includes a
chloroprene polymer latex (A) and an isoprene polymer latex (B), in
which the chloroprene polymer has a z-average particle size of 180
nm or greater and smaller than 300 nm, and a
tetrahydrofuran-insoluble fraction of 80 to 99% by mass; the
chloroprene polymer latex (A) is (1) a copolymer latex of
chloroprene (A-1) and 2,3-dichloro-1,3-butadiene (A-2-1), or (2) a
copolymer latex of the above (A-1) and (A-2-1), and another monomer
(A-2-2); and the copolymer is obtained by copolymerization in which
the ratio of 2,3-dichloro-1,3-butadiene (A-2-1) is 5.0 to 30.0% by
mass relative to the total amount of the monomer components
chloroprene (A-1) and 2,3-dichloro-1,3-butadiene (A-2-1) of 100% by
mass. The isoprene-based polymer latex composition's quality is
maintained, and the properties after cross-linking of a molded
product obtained by dipping a dipping former into the composition
multiple times do not deteriorate.
Inventors: |
OGAWA; Masahiro; (Minato-ku,
Tokyo, JP) ; MURATA; Tomoaki; (Minato-ku, Tokyo,
JP) ; OGAWA; Noriko; (Minato-ku, Tokyo, JP) ;
KAMIJO; Masanao; (Minato-ku, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHOWA DENKO K.K. |
Minato-ku, Tokyo |
|
JP |
|
|
Assignee: |
SHOWA DENKO K.K.
Minato-ku, Tokyo
JP
|
Family ID: |
71521176 |
Appl. No.: |
17/421149 |
Filed: |
November 26, 2019 |
PCT Filed: |
November 26, 2019 |
PCT NO: |
PCT/JP2019/046125 |
371 Date: |
July 7, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 2003/2296 20130101;
B29C 41/003 20130101; C08F 136/08 20130101; C08L 2205/18 20130101;
C08L 93/04 20130101; C08F 236/18 20130101; B29L 2031/4864 20130101;
C08K 5/0025 20130101; C08L 11/02 20130101; C08K 5/005 20130101;
C08K 3/22 20130101; C08L 2201/52 20130101; C08F 236/18 20130101;
C08F 236/18 20130101; C08F 236/18 20130101; C08F 2/26 20130101 |
International
Class: |
C08F 136/08 20060101
C08F136/08; C08L 11/02 20060101 C08L011/02; C08L 93/04 20060101
C08L093/04; C08K 3/22 20060101 C08K003/22; C08K 5/00 20060101
C08K005/00; B29C 41/00 20060101 B29C041/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 10, 2019 |
JP |
2019-002653 |
Claims
1. An isoprene-based polymer latex composition comprising a
chloroprene polymer latex (A), an isoprene polymer latex (B), and
an emulsifier (C), wherein the chloroprene polymer latex has a
z-average particle size of chloroprene polymer particles contained
therein of 180 nm or greater and smaller than 300 nm and a
tetrahydrofuran insoluble fraction of 80 to 99% by mass, the
chloroprene polymer latex (A) is (1) a copolymer latex of
chloroprene (A-1) and 2,3-dichloro-1,3-butadiene (A-2-1), or (2) a
copolymer latex of chloroprene (A-1), 2,3-dichloro-1,3-butadiene
(A-2-1), and another monomer (A-2-2), and the copolymer is obtained
by copolymerization in which the ratio of
2,3-dichloro-1,3-butadiene (A-2-1) is 5.0 to 30.0% by mass relative
to the total amount of the monomer components chloroprene (A-1) and
2,3-dichloro-1,3-butadiene (A-2-1) of 100% by mass.
2. The isoprene-based polymer latex composition according to claim
1, comprising at least one of a metal oxide (D), a cross-linking
accelerator (E), and an antioxidant (F).
3. The isoprene-based polymer latex composition according to claim
1, wherein the emulsifier (C) is an anionic surfactant.
4. The isoprene-based polymer latex composition according to claim
1, wherein the emulsifier (C) contains a rosin acid soap obtained
by saponifying a rosin acid with sodium hydroxide and/or potassium
hydroxide in an excess amount relative to the rosin acid.
5. The isoprene-based polymer latex composition according to claim
2, comprising, relative to 100 parts by mass of solid content
contained in the isoprene-based polymer latex composition, the
emulsifier (C) in a ratio of 1.0 to 30.0 parts by mass, the metal
oxide (D) in a ratio of 0.1 to 20.0 parts by mass, the
cross-linking accelerator (E) in a ratio of 0.1 to 10.0 parts by
mass, and the antioxidant (F) in a ratio of 0.1 to 10.0 parts by
mass.
6. The isoprene-based polymer latex composition according to claim
1, wherein the mass ratio of the solid content contained in the
chloroprene polymer latex (A) to the solid content contained in the
isoprene polymer latex (B) is 50:50 to 1:99.
7. The isoprene-based polymer latex composition according to claim
1, wherein the film forming rate of the chloroprene polymer latex
is 0.15 mm/min or higher and 0.50 mm/min or lower.
8. The isoprene-based polymer latex composition according to claim
1, wherein the film forming rate of the chloroprene polymer latex
is 41% or higher relative to the film forming rate of the isoprene
polymer latex to be mixed.
9. The isoprene-based polymer latex composition according to claim
1, wherein the chloroprene polymer latex has a pH value of 10.5 or
higher and 14.0 or lower.
10. The isoprene-based polymer latex composition according to claim
1, wherein the isoprene polymer particles in the isoprene polymer
latex have a z-average particle size of 300 nm or greater and 1,000
nm or smaller.
11. A dip-molded product obtained by curing the isoprene-based
polymer latex composition according to claim 1 by a dip-molding
method.
12. The dip-molded product according to claim 11, which is a
disposable rubber glove.
13. The isoprene-based polymer latex composition according to claim
2, wherein the mass ratio of the solid content contained in the
chloroprene polymer latex (A) to the solid content contained in the
isoprene polymer latex (B) is 50:50 to 1:99.
14. The isoprene-based polymer latex composition according to claim
2, wherein the film forming rate of the chloroprene polymer latex
is 0.15 mm/min or higher and 0.50 mm/min or lower.
15. The isoprene-based polymer latex composition according to claim
2, wherein the film forming rate of the chloroprene polymer latex
is 41% or higher relative to the film forming rate of the isoprene
polymer latex to be mixed.
16. The isoprene-based polymer latex composition according to claim
2, wherein the chloroprene polymer latex has a pH value of 10.5 or
higher and 14.0 or lower.
17. The isoprene-based polymer latex composition according to claim
2, wherein the isoprene polymer particles in the isoprene polymer
latex have a z-average particle size of 300 nm or greater and 1,000
nm or smaller.
18. A dip-molded product obtained by curing the isoprene-based
polymer latex composition according to claim 2 by a dip-molding
method.
Description
TECHNICAL FIELD
[0001] The present invention relates to an isoprene-based polymer
latex composition comprising a chloroprene polymer latex and an
isoprene polymer latex. The isoprene-based polymer latex
composition according to the present invention maintains the ratio
of both polymer latexes therein contained even after the repeated
dipping of a former during the production process of molded
products by a dip-molding method, and enables molded products
obtained in the multiple-time dipping to have physical properties
with no deterioration between those molded products, for example,
medical gloves and other products to have post cross-linked
physical properties with no deterioration between those
products.
BACKGROUND ART
[0002] A chloroprene polymer is a crystalline high-molecular rubber
that contains chlorine. Among various types of rubbers, chloroprene
polymers have a good balance of physical properties such as
chemical resistance, heat resistance, and weatherability, and are
used for a broad range of applications such as glove products.
[0003] However, chloroprene polymers generally require high
temperature conditions at 120 to 130.degree. C. for cross-linking,
and exhibit poor energy efficiency during cross-linking compared
with rubbers such as natural rubber and isoprene polymers which are
cross-linked at a temperature of 100 to 110.degree. C. Chloroprene
polymers cross-linked at a temperature of 100 to 110.degree. C.
contain many parts remaining uncross-linked, causing serious
deterioration in breaking strength. For this reason, their improved
productivity and cross-linking physical properties have been
required for the production of products such as gloves by a
dip-molding method.
[0004] A method is known in which natural rubber, or a synthetic
rubber such as an isoprene rubber being cross-linkable at a
temperature of 100 to 110.degree. C., is mixed with a chloroprene
polymer to improve the various mechanical properties thereof.
[0005] However, there is a problem such that multiple-time dipping
in a composition obtained by mixing a chloroprene polymer with
another rubber causes a change in the ratio of rubber components
contained in the mixed composition due to the film forming rates
varying in accordance with the types of rubber, resulting in
unstable mechanical properties of obtained molded products.
[0006] For example, JP 2017-508840 A (Patent Literature 1)
discloses that a glove product having a breaking strength of 18 to
25 MPa is obtained by using a composition comprising 40 to 60% by
mass of an isoprene rubber relative to 40 to 60% by mass of a
chloroprene rubber, and being free of diphenyl guanidine. Patent
Literature 1 describes only the mechanical properties of
cross-linked molded products obtained by a single dipping
operation, not referring to whether cross-linked molded products
obtained by multiple-time dipping operations also exhibit
equivalent mechanical properties.
CITATION LIST
Patent Literature
[0007] Patent Literature 1: JP 2017-508840 A (U.S. Ser. No.
10/253,170 B2)
SUMMARY OF INVENTION
Technical Problem
[0008] In view of the above problems, the object of the present
invention is to provide a composition comprising a chloroprene
polymer latex and an isoprene polymer latex (hereinafter referred
to as an isoprene-based polymer latex composition in the present
description) that maintains the quality thereof during a dipping
step, and prevents the deterioration in the cross-linking physical
properties of molded products obtained by the dipping of a dipping
former multiple times in the above composition.
Solution to Problem
[0009] As a result of earnest studies to achieve the above object,
the present inventors have focused on the different film forming
rates of a chloroprene polymer latex and an isoprene polymer latex,
and found that the quality of obtained rubber molded products does
not deteriorate even after multiple-time dipping operations, when
the z-average particle size of a chloroprene polymer is adjusted
within a specific range, thereby completing the present
invention.
[0010] Namely, the present invention relates to an isoprene-based
polymer latex composition and dip-molded products as described
below.
[0011] [1]
[0012] An isoprene-based polymer latex composition comprising a
chloroprene polymer latex (A), an isoprene polymer latex (B), and
an emulsifier (C), wherein the chloroprene polymer latex has a
z-average particle size of chloroprene polymer particles contained
therein of 180 nm or greater and smaller than 300 nm and a
tetrahydrofuran insoluble fraction of 80 to 99% by mass, the
chloroprene polymer latex (A) is (1) a copolymer latex of
chloroprene (A-1) and 2,3-dichloro-1,3-butadiene (A-2-1), or (2) a
copolymer latex of chloroprene (A-1), 2,3-dichloro-1,3-butadiene
(A-2-1), and another monomer (A-2-2), and the copolymer is obtained
by copolymerization in which the ratio of
2,3-dichloro-1,3-butadiene (A-2-1) is 5.0 to 30.0% by mass relative
to the total amount of the monomer components chloroprene (A-1) and
2,3-dichloro-1,3-butadiene (A-2-1) of 100 by mass.
[0013] [2]
[0014] The isoprene-based polymer latex composition described in
[1], comprising at least one of a metal oxide (D), a cross-linking
accelerator (E), and an antioxidant (F).
[0015] [3]
[0016] The isoprene-based polymer latex composition described in
[1], wherein the emulsifier (C) is an anionic surfactant.
[0017] [4]
[0018] The isoprene-based polymer latex composition described in
[1], wherein the emulsifier (C) contains a rosin acid soap obtained
by saponifying a rosin acid with sodium hydroxide and/or potassium
hydroxide in an excess amount relative to the rosin acid.
[0019] [5]
[0020] The isoprene-based polymer latex composition described in
any one [2] to [4], comprising, relative to 100 parts by mass of
solid content contained in the isoprene-based polymer latex
composition, the emulsifier (C) in a ratio of 1.0 to 30.0 parts by
mass, the metal oxide (D) in a ratio of 0.1 to 20.0 parts by mass,
the cross-linking accelerator (E) in a ratio of 0.1 to 10.0 parts
by mass, and the antioxidant (F) in a ratio of 0.1 to 10.0 parts by
mass.
[0021] [6]
[0022] The isoprene-based polymer latex composition described in
any one of [1] to [5], wherein the mass ratio of the solid content
contained in the chloroprene polymer latex (A) to the solid content
contained in the isoprene polymer latex (B) is 50:50 to 1:99.
[0023] [7]
[0024] The isoprene-based polymer latex composition described in
any one of [1] to [6], wherein the film forming rate of the
chloroprene polymer latex is 0.15 mm/min or higher and 0.50 mm/min
or lower.
[0025] [8]
[0026] The isoprene-based polymer latex composition described in
any one of [1] to [7], wherein the film forming rate of the
chloroprene polymer latex is 41 or higher relative to the film
forming rate of the isoprene polymer latex to be mixed.
[0027] [9]
[0028] The isoprene-based polymer latex composition described in
any one of [1] to [8], wherein the chloroprene polymer latex has a
pH value of 10.5 or higher and 14.0 or lower.
[0029] [10]
[0030] The isoprene-based polymer latex composition described in
any one of [1] to [9], wherein the isoprene polymer particles in
the isoprene polymer latex have a z-average particle size of 300 nm
or greater and 1,000 nm or smaller.
[0031] [11]
[0032] A dip-molded product obtained by curing the isoprene-based
polymer latex composition described in any one of [1] to [10] by a
dip-molding method.
[0033] [12]
[0034] The dip-molded product described in [11], which is a
disposable rubber glove.
Advantageous Effects of Invention
[0035] The isoprene-based polymer latex composition according to
the present invention maintains the quality of the composition even
after the repeated dipping of a former by a dip-molding method, and
also maintains the cross-linking properties of the molded product
which is a dip-molded product, resulting in the obtainment of a
molded product having stable performance.
DESCRIPTION OF EMBODIMENTS
[0036] Embodiments of the present invention are described in detail
below.
[0037] The isoprene-based polymer latex composition according to
the present invention comprises a chloroprene polymer latex (A), an
isoprene polymer latex (B), and an emulsifier (C), and a
chloroprene polymer contained in the chloroprene polymer latex has
a z-average particle size of 180 nm or greater and smaller than 300
nm.
[0038] The isoprene-based polymer latex composition according to
the present invention may comprise at least one of a metal oxide
(D), a cross-linking accelerator (E), and an antioxidant (F).
[0039] An embodiment of components of the isoprene-based polymer
latex composition according to the present invention and the
z-average particle size of the chloroprene polymer are described in
detail below.
[0040] The isoprene-based polymer latex composition according to
the present invention comprises, as polymer latex components, a
chloroprene polymer latex which has a specific structure and an
isoprene polymer latex.
[0041] Chloroprene Polymer Latex (A):
[0042] In the present description, a chloroprene polymer latex (A)
having a specific structure means (1) a copolymer latex of
chloroprene (A-1) and 2,3-dichloro-1,3-butadiene (A-2-1), or (2) a
copolymer latex of chloroprene (A-1), 2,3-dichloro-1,3-butadiene
(A-2-1), and another monomer (A-2-2).
[0043] Relative to the total amount of 2-chloro-1,3-butadiene
(chloroprene) (A-1) and 2,3-dichloro-1,3-butadiene (A-2-1) of 100
parts by mass, the ratio of 2,3-dichloro-1,3-butadiene (A-2-1) as a
monomer component of the copolymer is 5.0 to 30.0 parts by mass,
preferably 7.0 to 24.0 parts by mass, and more preferably 8.5 to
15.0 parts by mass. When the ratio of (A-2-1) is 5.0 parts by mass
or higher, the temporal stability of flexibility is well improved,
and when the ratio is 30.0 parts by mass or lower, polymer
crystallization is suppressed and good flexibility is obtained.
[0044] Examples of another copolymerizable monomer component
(A-2-2) are 1-chloro-1,3-butadiene, butadiene, isoprene, styrene,
acrylonitrile, acrylic acid and the esters thereof, and methacrylic
acid and the esters thereof. The ratio is, relative to 100 parts by
mass of 2-chloro-1,3-butadiene (chloroprene) (A-1), preferably 0.1
to 20.0 parts by mass, more preferably 0.5 to 15.0 parts by mass,
and still more preferably 1.0 to 10.0 parts by mass. Depending on
necessity, 2 or more of the monomer components may be used. By
determining the ratio of (A-2-2) relative to 100 parts by mass of
(A-1) to be 20.0 parts by mass or lower, the temporal stability of
flexibility, in addition to tensile strength and elongation, of
dip-molded products can be well maintained.
[0045] Method for Polymerizing Chloroprene Polymer Latex (A):
[0046] As a method for polymerizing a chloroprene polymer latex
(A), emulsion polymerization may be adopted, and aqueous emulsion
polymerization is particularly preferred from industrial
viewpoints.
[0047] Emulsifier (C) Used in Polymerization of Chloroprene Polymer
Latex (A):
[0048] As the emulsifier (C), an anionic surfactant is preferred.
Examples of anionic surfactants are an alkali metal salt of a
disproportionated rosin acid, dodecylbenzenesulfonates (such as a
sodium salt of dodecylbenzenesulfonic acid, and a triethanolamine
salt of dodecylbenzenesulfonic acid), diphenylethersulfonates (such
as a sodium salt of diphenylethersulfonic acid, and an ammonium
salt of diphenylethersulfonic acid), naphthalenesulfonates (such as
a sodium salt of a S-naphthalenesulfonic acid formaldehyde
condensate), fatty acid alkali metal salts (such as potassium
laurate), and polyoxyalkylene alkyl ether sulfonates (such as
sodium polyoxyethylene alkyl ether sulfonate). Among the anionic
surfactants above, an ordinary rosin acid soap is preferably used
in terms of simple and convenient solidification operations. From
the viewpoint of coloring stability, a sodium or a potassium salt
of a disproportionated rosin acid is particularly preferred.
[0049] The use amount of the emulsifier (C) is, relative to 100
parts by mass of solid content contained in the isoprene-based
polymer latex, preferably 1.0 to 30.0 parts by mass, more
preferably 2.0 to 20.0 parts by mass, and still more preferably 3.0
to 10.0 parts by mass. When the use amount is 1.0 part by mass or
higher, stable emulsification is performable, and heat generation
during polymerization is well controlled, aggregate formation is
suppressed, and good product appearance is obtained, for example.
Mechanical stability is also improved and aggregate formation is
suppressible at the time of mixing with a chloroprene polymer.
[0050] When the use amount is 30.0 parts by mass or lower, a low
adhesive polymer containing a lesser amount of an emulsifier
remaining therein is obtained, and a mold (former) is easily
detached during the molding of a component, resulting in good
workability and operability. Good color tones of products are also
obtained.
[0051] Emulsifiers may be used in combination of 2 or more
thereof.
[0052] Polymerization Initiator Used for Polymerizing Chloroprene
Polymer Latex (A):
[0053] Generic radical polymerization initiators, which are not
particularly limited, may be used. Preferred examples of
polymerization initiators used in emulsion polymerization are
specifically organic or inorganic peroxides such as benzoyl
peroxide, potassium persulfate, and ammonium persulfate; and azo
compounds such as azobisisobutyronitrile. Promoters such as
anthraquinone sulfonate, potassium sulfite, and sodium sulfite may
be used simultaneously, if appropriate. The radical polymerization
initiators and promoters as such may be used in combination of 2 or
more thereof.
[0054] Polymerization Terminator Used in Polymerizing Chloroprene
Polymer Latex (A):
[0055] For terminating the polymerization of the chloroprene
polymer latex (A), generic terminators, which are not particularly
limited, may be used. Preferred examples are specifically
phenothiazine, para-t-butylcatechol, hydroquinone, hydroquinone
monomethyl ether, and diethylhydroxylamine. The polymerization
terminators as such may be used in combination of 2 or more
thereof.
[0056] Polymerization Conversion of Chloroprene Polymer Latex
(A):
The polymerization conversion of the chloroprene polymer latex (A)
is preferably 65% or higher, more preferably 70% or higher, and
still more preferably 74% or higher. At a polymerization conversion
of 65% or higher, there is a sufficient amount of tetrahydrofuran
insoluble component in the solid content, resulting in good
physical properties of a cross-linked film during molding using a
chloroprene polymer alone and during molding using a mixture of a
chloroprene polymer and an isoprene polymer.
[0057] Z-Average Particle Size of Chloroprene Polymer
Particles:
[0058] According to the present invention, the z-average particle
size of a chloroprene polymer which is a main polymer component of
the isoprene-based polymer latex composition is adjusted within a
specific range (of 180 nm or greater and smaller than 300 nm).
Thereby the quality of the isoprene-based polymer latex composition
which is used in a repeated dipping step is maintained, and the
isoprene-based polymer latex composition suppressing the
deterioration in the cross-linking physical properties of molded
products that are obtained by the multiple-time dipping of a
dipping former in the composition is obtainable.
[0059] In the present description, the z-average particle size of
chloroprene polymer particles contained in the chloroprene polymer
latex (A) is obtained by measuring a solution of the latex diluted
with pure water to 0.1% by mass with a dynamic light scattering
photometer (ZETASIZER.RTM. Nano-S, produced by Malvern Panalytical
Ltd). An anionic chloroprene polymer latex using a rosin acid soap
as an emulsifier ordinarily has a z-average particle size of 148 to
320 nm. According to the present invention, the z-average particle
size of a chloroprene polymer is controlled to 180 nm or greater
and smaller than 300 nm, preferably 190 nm or greater and smaller
than 280 nm, and more preferably 200 nm or greater and smaller than
260 nm by adjusting the amount of a rosin acid and the amounts of
emulsifiers relative to the parts by mass of monomers.
[0060] In order to achieve the z-average particle size targeted by
the present invention, it is desirable to add a rosin acid which is
a raw material of a rosin acid soap in an amount of 1.8 to 3.4
parts by mass relative to 100 parts by mass of the total amount of
monomers constituting the chloroprene polymer latex (A).
[0061] When the z-average particle size is 180 nm or greater,
dehydrochlorination from the chloroprene polymer latex (A) is
suppressed and stability of the chloroprene polymer latex (A) is
obtained, resulting in suppressed aggregate formation. When the
z-average particle size is 300 nm or smaller, a rosin acid soap in
an amount sufficient for preferred emulsification is obtained and
thus heat generation during polymerization is well controlled,
aggregate formation is suppressed, and good product appearance is
obtained.
[0062] An example of a method for adjusting a z-average particle
size of a polymer contained in the chloroprene polymer latex (A) is
a method of adjusting the amount of an emulsifier at the start of
polymerization. In general, when using the same emulsifier, the
lower the emulsifier concentration at the start of polymerization
is, the greater the z-average particle size is. For example, when
the amount of a rosin acid contained in a rosin acid soap is
determined to be 3.4 parts by mass relative to 100 parts by mass of
monomers, and a polymerization conversion is determined to be 90%
or higher, the z-average particle size is 150 nm. In contrast, when
the amount of a rosin acid is determined to be 2.5 parts by mass
and a polymerization conversion is determined to be 90% similarly,
the z-average particle size is 200 nm. Methods for particle size
adjustment are not limited to the above exemplified one. The
z-average particle size may also be adjusted by methods different
from the above exemplified one, for example by a method of changing
the types of emulsifiers or by a method of further adding a
monomer.
[0063] Tetrahydrofuran Insoluble Fraction of Chloroprene Polymer
Latex (A):
[0064] The tetrahydrofuran insoluble fraction of the chloroprene
polymer latex (A) is preferably 80 to 99% by mass, and more
preferably 88 to 95% by mass. The tetrahydrofuran insoluble
fraction of lower than 80% by mass is not preferred since
detachment from a former during molding is difficult due to
decreased cross-linking rates and deteriorated breaking strength.
The breaking strength of molded products produced from a mixture
with an isoprene polymer is deteriorated as well. When the
tetrahydrofuran insoluble fraction is higher than 99% by mass, the
polymer becomes brittle with reduced flexibility and deteriorated
breaking strength and tensile elongation.
[0065] The tetrahydrofuran insoluble fraction is evaluated by the
method below.
[0066] A chloroprene polymer latex in an amount of 1 g is added
dropwise to 100 mL of tetrahydrofuran, and is shaken for 24 hours.
The obtained mixture is thereafter subjected to centrifugal
separation with a centrifuge (high-speed cooling centrifuge H-9R,
produced by Kokusan Co., Ltd.) at 14,000 rpm for 60 minutes, and a
supernatant dissolved phase is obtained. The dissolved phase is
evaporated/dried and solidified at a temperature of 100.degree. C.
for 1 hour, and the mass of the obtained dry solid matter is
measured.
Tetrahydrofuran insoluble fraction (%)={1-[(tetrahydrofuran
dissolved amount)/(amount of solid content in 1 g of chloroprene
copolymer latex)]}.times.100
[0067] Solid content is measured by the method described in
Examples.
[0068] The pH value of the chloroprene polymer latex at a
temperature of 25.degree. C. is preferably 10.5 or higher and 14.0
or lower, more preferably 11.5 or higher and 13.9 or lower, and
still more preferably 12.5 or higher and 13.8 or lower. Chloroprene
polymer latexes having a pH value within the above range are
preferred since an anionic surfactant which is an emulsifier is
stable and aggregate formation is suppressible.
[0069] The Brookfield viscosity of the chloroprene polymer latex is
preferably 5.0 mPas or higher and 90.0 mPas or lower, more
preferably 6.0 mPas or higher and 60.0 mPas or lower, and still
more preferably 9.0 mPas or higher and 40.0 mPas or lower.
Chloroprene polymer latexes having a Brookfield viscosity of 90.0
mPas or lower are preferred in terms of easy handling due to
appropriate viscosity. Chloroprene polymer latexes having a
Brookfield viscosity of 5.0 mPas or higher are also preferred due
to mixed additives (such as a cross-linking agent, a cross-linking
accelerator, and a preservative) diffusing in the latexes at high
rates and shortened maturation time.
[0070] The weight average molecular weight Mw of the chloroprene
polymer is preferably 300,000 to 3,000,000, more preferably 500,000
to 2,500,000, and still more preferably 700,000 to 2,000,000.
Chloroprene polymers having a weight average molecular weight Mw of
300,000 or higher are preferred since good breaking strength is
obtained by cross-linking. Chloroprene polymers having a weight
average molecular weight Mw of 2,000,000 or lower are also
preferred since suitable hardness is obtained due to a cross-linked
film with suppressed hardening.
[0071] Isoprene Polymer Latex (B):
[0072] Isoprene polymers constituting the isoprene polymer latex
(B) used in the present invention are not particularly limited and
may be a homopolymer of an isoprene monomer alone or copolymers of
an isoprene monomer as a main monomer component and another monomer
copolymerizable with isoprene.
[0073] Examples of another monomer copolymerizable with isoprene
are 1,3-butadiene, styrene, chloroprene, methacrylic acid, methyl
methacrylate, acrylic acid, methyl acrylate, acrylonitrile,
acrylamide, vinyl chloride, vinyl acetate, N-vinylpyrrolidone,
vinylidene chloride, and vinylidene fluoride.
[0074] The weight average molecular weight Mw of the isoprene
polymer is preferably 500,000 to 5,000,000, more preferably 550,000
to 4,500,000, and still more preferably 600,000 to 4,000,000.
Isoprene polymers having a weight average molecular weight Mw of
500,000 or higher are preferred since good breaking strength is
obtained by cross-linking. Isoprene polymers having a weight
average molecular weight Mw of 5,000,000 or lower are also
preferred since the hardening of a cross-linked film is suppressed
and suitable hardness is obtained.
[0075] The tetrahydrofuran insoluble fraction of the isoprene
polymer latex is 0% by mass to 30% by mass, preferably 0% by mass
to 25% by mass, and more preferably 0% by mass to 20% by mass. The
isoprene polymer latexes having a tetrahydrofuran insoluble
fraction within the above range are preferred since the number of
sites reacted with a cross-linking agent is appropriate, good
cross-linking rates are obtained, and mechanical properties after
cross-linking are excellent.
[0076] The pH value of the isoprene polymer latex at a temperature
of 25.degree. C. is preferably 9.0 to 13.0, more preferably 9.5 to
12.5, and still more preferably 10.0 to 12.0. The isoprene polymer
latexes having pH values within the above range are preferred since
an anionic surfactant which is an emulsifier is stable and
aggregate formation is suppressible.
[0077] The Brookfield viscosity of the isoprene polymer latex is
preferably 20 mPas to 100 mPas, more preferably 25 mPa's to 95
mPas, and still more preferably 25 mPas to 90 mPas. Isoprene
polymer latexes having a Brookfield viscosity of 100 mPa's or lower
are preferred in terms of easy handling due to appropriate
viscosity. Isoprene polymer latexes having a Brookfield viscosity
of 20 mPas or higher are also preferred due to mixed additives
(such as a cross-linking agent, a cross-linking accelerator, and a
preservative) diffusing in the latexes at high rates and shortened
maturation time.
[0078] For the isoprene-based polymer latex composition according
to the present invention, at least one or preferably three
additives selected from a metal oxide (D), a cross-linking
accelerator (E), and an antioxidant (F) are preferably added to the
chloroprene polymer latex and the isoprene polymer latex before
mixing both latexes. By adding the above, an isoprene-based polymer
latex composition enabling the formation of dip-molded products
having sufficient tensile strength and flexibility is obtained.
Among components to be added, water-insoluble components or
components destabilizing the colloid state of the latex are made
into aqueous dispersions beforehand, which are then added to each
of the copolymer latexes.
[0079] Metal Oxide (D):
[0080] Since chloroprene polymers are generally prone to
deterioration caused by oxygen, a metal oxide is preferably added
for the purpose of acid acceptance or oxidation prevention. The
metal oxide is not particularly limited and specific examples are
zinc oxide, lead dioxide, and trilead tetraoxide. The above may be
used in combination of 2 or more. By the use with cross-linking
accelerators below, cross-linking is more effectively performable.
The addition amount of those metal oxides is preferably 0.1 to 20.0
parts by mass, more preferably 0.5 to 15.0 parts by mass, and still
more preferably 1.0 to 10.0 parts by mass, relative to 100 parts by
mass of solid content contained in each of the polymer latexes. By
adding a metal oxide in an amount of 0.1 parts by mass or higher, a
sufficient cross-linking rate is obtained. By adding a metal oxide
in an amount of 20.0 parts by mass or lower, good cross-linking is
achieved and scorching is suppressed. In addition, the polymer
latex composition exhibits improved colloid stability, barely
causing problems such as sedimentation.
[0081] In the isoprene-based polymer latex composition according to
the present invention, a generic cross-linking agent, which is not
particularly limited, may be used. Cross-linking agents such as
sulfur, a sulfur compound, and an organic peroxide may be used.
These may be used in combination of 2 or more thereof.
[0082] Cross-Linking Accelerator (E):
[0083] According to the present invention, a cross-linking
accelerator is preferably used. Usable cross-linking accelerators
are ones which are generally used in cross-linking isoprene-based
polymer latexes and are based on thiuram, dithiocarbamate,
thiourea, or guanidine, and thiuram-based ones are preferred.
Examples of thiuram-based cross-linking accelerators are
tetraethylthiuram disulfide, and tetrabutylthiuram disulfide.
Examples of dithiocarbamate-based cross-linking accelerators are
sodium dibutylthiodicarbamate, zinc dibutylthiodicarbamate, and
zinc diethylthiodicarbamate. Examples of thiourea-based
cross-linking accelerators are ethylenethiourea, diethylthiourea,
trimethylthiourea, and N,N'-diphenylthiourea, and
N,N'-diphenylthiourea is particularly preferred. Examples of
guanidine-based cross-linking accelerators are diphenyl guanidine,
and di-o-tolylguanidine. The above cross-linking accelerators may
be used in combination of 2 or more thereof. The addition amount of
those cross-linking accelerators is preferably 0.1 to 10.0 parts by
mass, more preferably 0.2 to 7.0 parts by mass, and still more
preferably 0.3 to 5.0 parts by mass, relative to 100 parts by mass
of solid content contained in each of the latexes. By adding a
cross-linking accelerator in an amount of 0.1 parts by mass or
higher, sufficient acceleration effects are obtained. By adding a
cross-linking accelerator in an amount of 10.0 parts by mass or
lower, a good cross-linking rate is achieved, cross-linking is
easily managed due to suppressed scorching, and products having
good mechanical properties such as tensile properties after
cross-linking are obtained.
[0084] In cases where cross-linking by using a cross-linking
accelerator alone is insufficient, a cross-linking agent is
ordinarily used simultaneously. Preferred examples of cross-linking
agents are sulfur-based cross-linking agents (such as powdery
sulfur, surface-treated sulfur, precipitated sulfur, colloidal
sulfur, and insoluble sulfur), and peroxide-based cross-linking
agents (such as di-t-butylperoxide, cumene hydroperoxide,
bis(.alpha.,.alpha.-dimethylbenzyl)peroxide, benzoylperoxide,
t-butylperbenzoate, 2,2-di-t-butylperoxybutane, and
azobisisobutyronitrile), and sulfur is particularly preferred. The
addition amount of a cross-linking agent is preferably 0.1 to 7.0
parts by mass, more preferably 0.2 to 5.0 parts by mass, and still
more preferably 0.3 to 3.0 parts by mass, relative to 100 parts by
mass of solid content contained in each of the latexes. By adding a
cross-linking agent in an amount of 0.1 parts by mass or higher,
sufficient acceleration effects are obtained, and by adding a
cross-linking agent in an amount of 7.0 parts by mass or lower, a
good cross-linking rate is obtained, cross-linking is easily
managed due to suppressed scorching, products having good heat
resistance after cross-linking are obtained, and bleeding barely
occurs.
[0085] Antioxidant (F):
[0086] With respect to antioxidants, an antioxidant for imparting
heat resistance (heat-resistant age resistor) and an
ozone-resistant antioxidant (ozone-resistant age resistor) must be
used in cases where ultimate heat resistance is required, and
preferably, both are used simultaneously. Heat-resistant age
resistors based on diphenylamines such as octylated diphenylamine,
p-(p-toluene-sulfonylamide)diphenylamine, and
4,4'-bis(.alpha.,.alpha.-dimethylbenzyl)diphenylamine are
preferably used due to their stain resistance (suppressed spread of
discoloration) in addition to their heat resistance. With respect
to ozone-resistant age resistors, N,N'-diphenyl-p-phenylenediamine
(DPPD) and N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD) are
preferably used. For products such as medical gloves in which
appearance, particularly a color tone and a hygiene property are
emphasized, however, hindered-phenolic antioxidants are normally
used preferably. The addition amount of an antioxidant is
preferably 0.1 to 10.0 parts by mass, more preferably 0.2 to 7.0
parts by mass, and still more preferably 0.3 to 5.0 parts by mass,
relative to 100 parts by mass of solid content contained in each of
the latexes. When the addition amount of an antioxidant is 0.1
parts by mass or higher, sufficient oxidation prevention effects
are obtained, and when the addition amount is 10.0 parts by mass or
lower, good cross-linking is achieved and a color tone does not
change. Thus, the addition amount within the above range is
preferred.
[0087] Preparation of Isoprene Polymer Latex Composition:
[0088] Before producing a molded product by a dip-molding method, a
chloroprene polymer latex and an isoprene polymer latex are mixed
to prepare an isoprene-based polymer latex composition.
[0089] According to the present invention, another polymer latex
may be contained in addition to a chloroprene polymer latex and an
isoprene polymer latex in an amount in which the object of the
present invention is not lost. Examples of another polymer latex
are acrylonitrile-butadiene rubber latex,
acrylonitrile-butadiene-styrene latex, acrylate latex, methacrylate
latex, styrene-butadiene rubber latex, chlorosulfonated
polyethylene latex, and natural rubber latex.
[0090] The mixing ratio of the chloroprene polymer latex (A) to the
isoprene polymer latex (B) in the isoprene-based polymer latex
composition according to the present invention ((A):(B)) is 50:50
to 1:99, more preferably 30:70 to 1:99, and still more preferably
15:85 to 5:95 in terms of the mass ratio of solid content contained
in the chloroprene polymer latex to solid content contained in the
isoprene polymer latex. When the mixing ratio is within the above
range, good breaking strength is achievable.
[0091] Film Forming Rate:
[0092] According to the present invention, the film forming rate of
a polymer latex (a chloroprene polymer latex, an isoprene polymer
latex, or an isoprene-based polymer latex composition) is evaluated
such that a former on which a 30% by mass aqueous calcium nitrate
solution as a coagulation liquid is adhered, is dipped in the latex
for 60 seconds, thereafter the obtained rubber molded product is
dried at a temperature of 70.degree. C. for 30 minutes to give a
dry rubber molded product, and from the film thickness of the
obtained dry rubber molded product, the film forming rate is
obtained based on the following formula.
Film forming rate (mm/min)=Film thickness of dry rubber molded
product (mm)/dipping time (min)
[0093] The film forming rate of a chloroprene polymer latex is
preferably 0.15 mm/min or higher and 0.50 mm/min or lower, more
preferably 0.18 mm/min or higher and 0.44 mm/min or lower, and
still more preferably 0.20 mm/min or higher and 0.30 mm/min or
lower. When the film forming rate of the chloroprene polymer latex
is 0.15 mm/min or higher, it slightly differs from the film forming
rate of an isoprene polymer latex, causing no compositional change
in the components constituting the mixture composition, and film
formation is performable without changing in the compositional
ratio. When the film forming rate is 0.50 mm/min or lower, the
z-average particle size of a chloroprene polymer latex is within a
good range, and good emulsification is achieved.
[0094] The film forming rate of a chloroprene polymer latex is
preferably 41% or higher relative to the film forming rate of an
isoprene polymer latex to be mixed, more preferably 42% or higher,
and is still more preferably 43% or higher.
EXAMPLES
[0095] The present invention is described by referring to examples
and comparative examples below, but is not limited thereto.
Example 1
[0096] Preparation of Chloroprene Polymer Latex and Composition
Thereof:
[0097] A reactor having an internal volume of 5 L was used, and
1.83 kg of 2-chloro-1,3-butadiene (chloroprene) (produced by Tokyo
Chemical Industry, Co., Ltd.), 0.17 kg of
2,3-dichloro-1,3-butadiene (produced by Tokyo Chemical Industry,
Co., Ltd.), 1.12 kg of pure water, 34 g of a rosin acid (R-300,
produced by Arakawa Chemical Industries, Ltd.), 106.6 g of a 20% by
mass aqueous potassium hydroxide solution (guaranteed reagent,
produced by FUJIFILM Wako Pure Chemical Corporation), 24 g of a
sodium salt of a .beta.-naphthalene sulfonate formaldehyde
condensate (produced by Kao Corporation), and 6.0 g of sodium
dodecyl benzene sulfonate (NEOPELEX.RTM. G-15, produced by Kao
Corporation) were fed into the reactor and emulsified. After the
rosin acid was converted into a rosin acid soap, polymerization was
performed for 5 hours in a nitrogen gas atmosphere at an initial
temperature of 40.degree. C., using potassium persulfate (1.sup.st
grade, produced by FUJIFILM Wako Pure Chemical Corporation) as an
initiator. When the polymerization conversion was confirmed to be
88 or higher, the polymerization was terminated. Subsequently,
unreacted monomers were eliminated via steam distillation to obtain
a chloroprene polymer latex (A). The pH value was 13.7, the Mw in
terms of polystyrene measured by GPC was 1,390,000, a chloroprene
polymer contained in the chloroprene polymer latex (A) had a
z-average particle size measured with a dynamic light scattering
photometer of 190 nm, the tetrahydrofuran insoluble fraction was
94.1%, the solid content was 52.9%, and the Brookfield viscosity
was 18 mPas.
[0098] To the chloroprene polymer latex (A) obtained above, a zinc
oxide dispersion, cross-linking accelerators, and a phenolic
antioxidant dispersion were added in the mixing ratios (parts by
mass relative to 100 parts by mass of dry solids of the latex)
shown in Table 1, and were mixed to prepare a chloroprene polymer
latex composition. The chloroprene polymer latex composition
exhibited a film forming rate of 0.21 mm/min.
[0099] The above polymerization conversion was obtained by the
method below.
[0100] A latex after polymerization was collected and dried at a
temperature of 141.degree. C. for 30 minutes to obtain solid
content, from which a polymerization conversion was calculated. The
solid content and polymerization conversion were obtained by the
following formulae.
Solid content after polymerization (% by mass)=[(mass after drying
at 141.degree. C. for 30 min.)/(mass of latex before
drying)].times.100
Polymerization conversion (%)=[(amount of formed polymer/feed
amount of chloroprene monomer)].times.100
[0101] Here, the amount of formed polymer was obtained by
subtracting the solid content other than the polymer from the solid
content after polymerization. As the solid content other than the
polymer, the amount of components not volatilizing under the
conditions at 141.degree. C. was calculated from the feed amount of
polymerization raw materials.
[0102] A z-average particle size of polymer particles contained in
a latex was obtained by measuring a solution obtained by diluting
the latex with pure water to have a concentration of 0.01 to 0.1%
by mass, with a dynamic light scattering photometer (ZETASIZER.RTM.
Nano-S, produced by Malvern Panalytical Ltd.)
[0103] Preparation of Isoprene Polymer Latex Composition:
[0104] As the isoprene polymer latex (B), Cariflex.RTM. IR0401SU
produced by Kraton Polymers Japan Limited was used. An isoprene
polymer contained in the latex had a z-average particle size of 680
nm. To the isoprene polymer latex (B), a zinc oxide dispersion,
cross-linking accelerators, a cross-linking agent (aqueous sulfur
dispersion), and a phenolic antioxidant dispersion were added in
the mixing ratios (parts by mass relative to 100 parts by mass of
dry solids of the latex) shown in Table 2, and were mixed to
prepare an isoprene polymer latex composition. The pH value was
11.3, and the Mw in terms of polystyrene measured by GPC was
3,180,000. The isoprene polymer latex (B) exhibited a film forming
rate of 0.44 mm/min.
[0105] Preparation of Isoprene-Based Polymer Latex Composition
(Mixture of Chloroprene Polymer Latex (A) and Isoprene Polymer
Latex (B)):
[0106] Both the above polymer latexes were fed into a stirring
vessel equipped with a Three-One Motor.RTM. in a ratio of the
chloroprene polymer latex:the isoprene polymer latex=10:90 (in
terms of parts by mass of dry solids) and were stirred at a
temperature of 23.degree. C. at 300 rpm for 5 minutes to be
homogeneously mixed. The composition after the stirring was left to
age at a temperature of 20.degree. C. for 24 hours. Before dipping
a former, the thus-obtained isoprene-based polymer latex
composition was fed into a stirring vessel equipped with a
Three-One Motor.RTM. and was stirred at a temperature of 23.degree.
C. at 300 rpm for 5 minutes for use.
Comparative Example 1
[0107] Preparation of Chloroprene Polymer Latex and Composition
Thereof for Comparison:
[0108] A reactor having an internal volume of 5 L was used, and
1.65 kg of 2-chloro-1,3-butadiene (chloroprene), 0.15 kg of
2,3-dichloro-1,3-butadiene, 1.45 kg of pure water, 77 g of a rosin
acid (R-300, produced by Arakawa Chemical Industries, Ltd.), 102.6
g of a 20% by mass aqueous potassium hydroxide solution, 18.7 g of
a 25% by mass aqueous sodium hydroxide solution, 9.5 g of a sodium
salt of a .beta.-naphthalene sulfonate formaldehyde condensate, and
1.08 g of n-dodecylmercaptan were fed into the reactor and
emulsified, and after the rosin acid was converted into a rosin
acid soap, polymerization was performed in a nitrogen gas
atmosphere at an initial temperature of 40.degree. C., using
potassium persulfate as an initiator. When the polymerization
conversion was confirmed to be 88% or higher, the polymerization
was terminated. Subsequently, unreacted monomers were eliminated
via steam distillation to obtain a chloroprene copolymer latex. A
chloroprene polymer in the chloroprene polymer latex had a
z-average particle size of 130 nm, the tetrahydrofuran insoluble
fraction was 37.2%, the solid content was 50.5%, and the Brookfield
viscosity was 16 mPas.
[0109] To the chloroprene polymer latex obtained above, a zinc
oxide dispersion, cross-linking accelerators, and a phenolic
antioxidant dispersion were added in the mixing ratios (parts by
mass relative to 100 parts by mass of dry solids of the latex)
shown in Table 2, and were mixed to prepare a chloroprene polymer
latex composition.
[0110] Using the same isoprene polymer latex as the one described
in Example 1, a mixed composition and a mixed molded product were
prepared in the same manner as described in Example 1. The
chloroprene polymer latex composition exhibited a film forming rate
of 0.18 mm/min.
[0111] Preparation and Cross-Linking of Dip-Molded Film:
[0112] Dip-molded films were prepared from the isoprene-based
polymer latex compositions prepared in Example 1 and Comparative
Example 1 by the method below.
[0113] A ceramic plate having a length of 200 mm, a width of 100
mm, and a thickness of 5 mm was used as a former of a dip-molded
film. The entire surface of the former was dipped in a 30% by mass
aqueous calcium nitrate solution as a coagulation liquid. After
being pulled up, the former was dried in an oven at a temperature
of 40.degree. C. for 5 minutes. The above operation was performed
on 10 formers.
[0114] The 10 formers were dipped in 400 g of each of the
isoprene-based polymer latex compositions and were pulled up in
order, and 10 sheets of films in total were formed. (Each of the
films are referred to as the 1.sup.st-prepared sample to the
10.sup.th-prepared sample.) The obtained films were dried in an
oven at a temperature of 70.degree. C. for 30 minutes.
Subsequently, the films were cross-linked by heating in an oven at
a temperature of 110.degree. C. for 30 minutes. After left to cool
at a temperature of 20.degree. C., the films were cut out from the
formers. Thereby cross-linked films were obtained.
[0115] Evaluation of Physical Properties after Cross-Linking:
[0116] The cross-linked sheets were each cut with a No. 6
dumbbell-shaped cutting blade specified in JIS-K6251-2017 to obtain
test pieces. The thickness of each test piece was adjusted to 0.15
to 0.25 mm.
[0117] Tensile Test
[0118] A tensile test after cross-linking and heat aging (at
110.degree. C. for 16 hours) was performed by a method in
accordance with JIS-K6251-2017. During the test, a modulus at 100%
elongation (M100), a modulus at 300% elongation (M300), a modulus
at 500% elongation (M500), a tensile strength (T.sub.B), and an
elongation (E.sub.B) at room temperature were measured. In
addition, the retention of tensile strength (T.sub.B) was obtained
based on the following formula.
T.sub.B retention (%)=(T.sub.B of the X.sup.th prepared
sample)/(T.sub.B of the 1.sup.st prepared sample).times.100
[0119] Viscosity:
[0120] A test sample was poured into a 300 mL polypropylene beaker
and bubbles included therein were completely eliminated. Using a
B-type viscometer specified in JIS K7117-1:1999, viscosity was
measured. Among the results obtained by continuous measurement, in
which the measured value was within 5%, the viscosity of the second
result was recorded.
[0121] Instrument: Viscometer, DV-E LVDVE115, produced by
BROOKFIELD
[0122] Spindle: No. 1 spindle
[0123] Velocity: 60 rpm
[0124] Temperature: 20.degree. C.
[0125] Tetrahydrofuran Insoluble Fraction:
[0126] Each of the isoprene polymer latexes in an amount of 1 g
(water content: 35 to 65% by mass) was added dropwise to 100 mL of
tetrahydrofuran, and was shaken with a shaker (SA300) produced by
Yamato Scientific Co., Ltd., for 10 hours. The obtained mixture was
thereafter subjected to centrifugal separation with a centrifuge
(H-9R, produced by Kokusan Co., Ltd.) at 14,000 rpm for 60 minutes,
and a supernatant dissolved phase was separated. Tetrahydrofuran
was evaporated at a temperature of 100.degree. C. for 1 hour to
obtain a dry solid matter, and the dissolved amount was calculated
and subtracted to obtain a tetrahydrofuran insoluble fraction (% by
mass).
[0127] Molecular Weight:
[0128] The supernatant dissolved phase after the centrifugal
separation at the time of measuring a gel content described above
was separated, diluted with tetrahydrofuran, and subjected to
molecular weight measurement in terms of polystyrene, by GPC (gel
permeation chromatography). Thereby a weight average molecular
weight (Mw) was measured. The GPC measurement conditions were
determined such that LC-20AD produced by Shimadzu Corporation was
used as a GPC measurement device, RID-10A (refractive index
detector) produced by Shimadzu Corporation was used as a detector,
the column type was PLgel 10 .mu.m MiniMIX-B produced by Agilent
Technologies Japan, Ltd., and tetrahydrofuran (for HPLC, produced
by Kanto Chemical Co., Inc.) was used as an eluting solution, at a
column temperature of 40.degree. C., and an outflow rate of 0.4
mL/min.
[0129] pH Values:
[0130] Using a benchtop pH meter F-71 (produced by Horiba, Ltd.),
pH values were measured at a sample temperature of 25.degree.
C.
[0131] Results are summarized in Tables 3 and 4.
TABLE-US-00001 TABLE 1 Components to be mixed Mixing ratio (parts
by mass) Chloroprene polymer latex 100 Zinc oxide dispersion.sup.1)
5 Cross-linking accelerator ZDBC.sup.2) 0.5 Cross-linking
accelerator ZMBT.sup.3) 0.5 Cross-linking accelerator DPG.sup.4)
0.25 Phenolic antioxidant dispersion.sup.5) 2 .sup.1)AZ-SW,
produced by Osaki Industry Co., Ltd. .sup.2)Nocceler .RTM. BZ,
produced by Ouchi Shinko Chemical Industrial Co., Ltd.
.sup.3)Nocceler .RTM. MZ, produced by Ouchi Shinko Chemical
Industrial Co., Ltd. .sup.4)Nocceler .RTM. D, produced by Ouchi
Shinko Chemical Industrial Co., Ltd. .sup.5)K-840, produced by
Chukyo Yushi Co., Ltd.
TABLE-US-00002 TABLE 2 Components to be mixed Mixing ratio (parts
by mass) Isoprene polymer latex 100 Zinc oxide dispersion.sup.1)
0.5 Sulfur.sup.6) 1.5 Cross-linking accelerator.sup.2) 0.5
Cross-linking accelerator.sup.3) 0.5 Cross-linking
accelerator.sup.4) 0.25 Phenolic antioxidant dispersion.sup.5) 2
.sup.1) to .sup.5)are the same as described in Table 1.
.sup.6)S-50, produced by Nippon Color Ind., Co., Ltd.
TABLE-US-00003 TABLE 3 Comparative Example 1 Example 1 Isoprene-
Film forming rate (mm/min) 0.21 0.18 based Z-average particle size
(nm) 190 130 polymer Tetrahydrofuran insoluble 94.1 37.2 latex
fraction (%) Solid content (%) 52.9 50.5 BF viscosity (mPa s) 18
16
TABLE-US-00004 TABLE 4 Example 1 Comparative Example 1 Number of
times of dipping 1.sup.st 3.sup.rd 7.sup.th 10.sup.th 1.sup.st
3.sup.rd 7.sup.th 10.sup.th time time time time time time time time
Mixing ratio of 10:90 10:90 10:90 10:90 10:90 10:90 10:90 10:90
chloroprene polymer latex:isoprene polymer latex (mass ratio)
Cross-linking 110 110 110 110 110 110 110 110 temperature (.degree.
C.) Cross-linking time 30 30 30 30 30 30 30 30 (min) M100 (MPa)
0.64 0.64 0.64 0.61 0.62 0.62 0.61 0.58 M300 (MPa) 1.10 1.13 1.20
1.10 1.20 1.10 1.20 1.10 M500 (MPa) 1.80 1.80 1.90 1.90 1.80 1.80
1.90 1.80 Eb (%) 1050 1050 1050 1050 1050 1050 1050 1050 Tb (MPa)
27.3 27.8 27.3 27.8 26.5 25.9 25.6 22.8 Tb retention relative 100
102 100 102 100 98 97 86 to the Tb of the 1.sup.st prepared sample
(%)
[0132] Table 4 shows that in Comparative Example 1 in which the
z-average particle size of the chloroprene polymer is smaller, the
more times dipping is performed, the lower the retention of Tb
relative to the Tb of the 1.sup.st-prepared sample is. Further
shown is that dip-molded products retaining constant properties are
not obtainable due to the compositional change in the
chloroprene-based polymer composition.
* * * * *